1. D/A conversion Semiconductors
The density of carriers in a semiconductor
For silicon at room temperature:
Drift current density: j = Qv, Q - charge density, v - velocity of charge in an electric field
jTdrift = jn + jp = q(n n + p p)E = E,  = q(n n + p p) (cm)-1 ,  = 1/ (cm)
Charge neutrality q(ND + p - NA - n) = 0; in thermal equilibrium: pn = ni2
For n-type: If (ND - NA) >> 2ni, n  (ND - NA)
Similarly for p-type.
Diffusion current , VT = kT/q, is approximately 25 mV,

2. Total current or

3. pn-junction and Diodes For reverse bias: - diode equation.
where IS = reverse saturation current (A) vD = voltage applied to diode (V) q = electronic charge (1.60 x C) k = Boltzmann’s constant (1.38 x J/K) T = absolute temperature n = nonideality factor (dimensionless) VT = kT/q = thermal voltage (V) (25 mV at room temp.)
IS is typically between and 10-9 A, and is strongly temperature dependent due to its dependence on ni2. The nonideality factor is typically close to 1

4. Rectifiers Half-wave Full wave